The present invention relates to a precise positioning actuator for a head element such as a thin-film magnetic head element or an optical head element, to a head gimbal assembly (HGA) with the actuator, to a disk drive apparatus with the HGA, to a manufacturing method of the actuator and to a manufacturing method of the HGA.
In a magnetic disk drive apparatus, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of HGAs, respectively.
Recently, recording and reproducing density along the radial direction or along the track width direction in the magnetic disk (track density) rapidly increase to satisfy the requirement for ever increasing data storage capacities and densities in today""s magnetic disk drive apparatus. For advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by a voice coil motor (VCM) only could not present enough accuracy.
In order to solve this problem, an additional actuator mechanism is mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be achieved by the VCM only. The techniques for achieving precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese patent publication No. 08180623 A.
As for the precise positioning actuator, there are various kinds of actuators such as a load beam structure actuator and a piggy-back structure actuator.
The load beam structure actuator is formed by mounting two PZT elements on a load beam of a suspension. These PZT elements are driven to assist each other so as to displace the load beam and thus a magnetic head slider mounted on the suspension is minutely displaced.
The piggy-back structure actuator is formed in integral by piezoelectric material of PZT in an I-character shape with one end section to be fixed to a suspension, the other end section to be fixed to a magnetic head slider and a pillar shaped movable arm connected between these end sections. By driving the PZT, the head slider is directly and minutely displaced. On the suspension, stepwise stacked are the actuator and the magnetic head slider, namely, the actuator is caught between the suspension and the slider to form a stacked cantilever structure.
However, such conventional structure actuators have following various problems:
(1) Mechanical resonance occurs at a relatively low frequency;
(2) Since the actuator as a whole consists of piezoelectric material such as PZT of a brittle material, shock resistance is very poor. Particularly, in case of the piggy-back structure actuator, since the actuator and the magnetic head slider are stacked to form a cantilever structure, a shock easily occurs with a moment and also shock resistance is extremely poor;
(3) Depending upon the size of the magnetic head slider, a travel of the magnetic head element during the precise positioning operation varies. Thus, sometimes, it is difficult to obtain enough stroke;
(4) Treatment of the actuator when assembling to form the HGA is very difficult;
(5) Particularly, in case of the piggy-back structure actuator, because of the stepwise stacked structure, a total thickness of the HGA around the magnetic head slider increases by the thickness of the actuator;
(6) Particularly, in case of the piggy-back structure actuator, because of three-dimensional and complicated attachment structure of the actuator, the handling at the time of an assembly of the HGA is very difficult and it is impossible to use a conventional HGA assembly equipment causing productivity to be very worse; and
(7) In case of the piggy-back structure actuator, in order not to interfere with the movement of the actuator, it is necessary to assemble with keeping a gap between the actuator and the magnetic head slider and also between the actuator and the suspension. However, forming of such gap will more decrease the shock resistance and it is difficult to precisely keep the gap constant. Particularly, since it is difficult to keep the suspension, the actuator and the magnetic head slider in parallel precisely, the head characteristics deteriorates.
It is therefore an object of the present invention to provide a precise positioning actuator for a head element, an HGA with the actuator, a disk drive apparatus with the HGA, a manufacturing method of the actuator and a manufacturing method of the HGA, whereby a mechanical resonance frequency can be increased.
Another object of the present invention is to provide a precise positioning actuator for a head element, an HGA with the actuator, a disk drive apparatus with the HGA, a manufacturing method of the actuator and a manufacturing method of the HGA, whereby a shock resistance can be greatly improved.
Further object of the present invention is to provide a precise positioning actuator for a head element, an HGA with the actuator, a disk drive apparatus with the HGA, a manufacturing method of the actuator and a manufacturing method of the HGA, whereby an enough stroke of the head element can be ensured.
Still further object of the present invention is to provide a precise positioning actuator for a head element, an HGA with the actuator, a disk drive apparatus with the HGA, a manufacturing method of the actuator and a manufacturing method of the HGA, whereby a productivity and also quality of the HGA can be greatly improved.
According to the present invention, a precise positioning actuator to be fixed to a head slider provided with at least one head element and to a support, for precisely positioning the at least one head element, includes a pair of movable arms formed by a metal plate. These movable arms are capable of displacing in response to a drive signal applied to the actuator along a direction crossing a plate plane of the movable arms, and catch the head slider in a space between them.
Since the movable arms are mainly made from a metal plate, the weight of the whole actuator can be reduced and thus a mechanical resonance frequency of the actuator can be increased. Also, as a basic member of the arms is formed by the metal plate that is strong and light-weighted, a shock resistance of the movable arms that are particularly weaken for the shock can be greatly improved. Due to the usage of the metal plate provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy. By using the metal plate to form the main portion of the actuator, the flexibility on a design of the actuator will improve with the shape and/or size. Thus, it is enabled to design the actuator with a sufficient stroke. Furthermore, because the metal plate can be precisely machined, accuracy in size of the actuator itself can be greatly improved.
Also, since the head slider is caught in a space between the movable arms that are capable of displacing in response to a drive signal applied thereto along a direction crossing a plate plane of the movable arms, the thickness of an HGA around the head slider does not increase even if the actuator is attached. Thus, no modifications in size of a disk drive apparatus due to the mounting of the actuator is necessary. Further, since the actuator and the head slider are not stacked to form a cantilever structure, a shock resistance can be greatly improved. Still further, since the head slider is caught in between the movable arms, the top end sections of the movable arms, which actually transfer the displacement to the head slider, can be extended to always position at the top end of the head slider. Thus, it is possible to provide a constant travel to the head slider even if its size changes, and therefore an enough stroke of the head element at the precise positioning operation can be always obtained.
It is preferred that the actuator includes a base made from a metal plate and fixed to the support, and that the movable arms extend from the base. As the base and the movable arms are made from a metal plate, the weight can be more reduced and a shock resistance can be more improved. Also, accuracy in size of the actuator itself can be greatly improved.
It is also preferred that the movable arms and the base have a structure formed by bending a single metal plate. Since the main portion of the actuator is configured by bending a single metal plate, its fabrication becomes easy and a mechanically strong actuator can be provided.
It is preferred that the movable arms have at their top end sections slider fixing sections to be fixed to side surfaces of the head slider, respectively. In this case, preferably, each of the slider fixing sections has a structure formed by bending the single metal plate inwardly.
It is also preferred that the actuator has a shape so that there exists Air gaps between the movable arms and side surfaces of the head slider except for the slider fixing sections, respectively.
It is preferred that each of the movable arms includes an arm member made of the metal plate, and a piezoelectric element formed or adhered on a side surface of the arm member. In this case, preferably, the piezoelectric element has a multilayer structure of piezoelectric material layers and of electrode layers, or a single layer structure of a piezoelectric material layer and of an electrode layer.
It is preferred that the metal plate is a stainless steel plate.
It is also preferred that the movable arms is constituted so that the head slider is linearly and laterally swayed in response to the drive signal. Since the head slider displaces namely sways with linear motion not swinging or rotational motion, more precise positioning of the head element can be expected.
It is further preferred that a spacing between the pair of movable arms is determined to a value slightly shorter than a width of the head slider to be caught.
Preferably, the at least one head element is at least one thin-film magnetic head element.
According to the present invention, also, an HGA includes a head slider provided with at least one head element, a support and aforementioned precise positioning actuator fixed to the head slider and to the support.
It is preferred that the movable arms of the actuator and the head slider are fixed by adhering.
It is also preferred that the actuator and the support are fixed by adhering or by laser welding.
According to the present invention, furthermore, a disk drive apparatus has at least one HGA mentioned above.
In addition, according to the present invention, a manufacturing method of a precise positioning actuator to be fixed to a head slider provided with at least one head element and to a support, for precisely positioning the at least one head element, includes a step of forming on a metal plate a plurality of conductor patterns connected to a plurality of piezoelectric elements, a step of cutting the metal plate into separated actuator members each including the conductor patterns and the piezoelectric elements for each actuator, and a step of bending each of the separated actuator members to form the individual actuator.
It is preferred that the forming step includes forming the plurality of piezoelectric elements and the plurality of conductor patterns by sputtering and by photolithography, or by printing and by sintering.
It is also preferred that the forming step includes forming the plurality of conductor patterns by sputtering and by photolithography or by printing and by sintering, and adhering the plurality of piezoelectric elements that are separately formed to the metal plate.
It is preferred that the cutting step includes cutting the metal plate into the separated actuator members each having a rough U-plane shape.
According to the present invention, further, a manufacturing method of an HGA includes a step of preparing a precise positioning actuator having a base formed by a metal plate and a pair of movable arms formed by a metal plate, the movable arms being extending from the base and capable of displacing in response to a drive signal applied thereto along a direction crossing a plate plane of the movable arms, a step of catching a head slider provided with at least one head element in a space between the movable arms of the actuator, and a step of fixing the base of the actuator with the caught head slider to a support.
First, the head slider is caught in a space between the movable arms of the actuator, and then the actuator with the caught head slider is fixed to the support. Since assembling of the head slider and the actuator can be carried out on the flat plate, alignment of the slider and the actuator becomes easy resulting that a higher accuracy assembling can be expected. Also, since a thermosetting adhesive with excellent curing performance although it needs a long curing time can be used, a high quality assembly of the head slider and the actuator can be obtained. Furthermore, since the assembly has a simple shape, adhesion and electrical connection of the assembly with a suspension can be performed by using a general HGA assembling equipment resulting the productivity to extremely improve and thus the manufacturing cost to reduce. In addition, due to the usage of the metal plate provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy.
Also, according to the present invention, a manufacturing method of an HGA includes a step of preparing a precise positioning actuator having a base formed by a metal plate and a pair of movable arms formed by a metal plate, the movable arms being extending from the base and capable of displacing in response to a drive signal applied thereto along a direction crossing a plate plane of the movable arms, a step of fixing the base of the actuator to a support, and a step of catching a head slider provided with at least one head element in a space between the movable arms of the actuator fixed to the support.
It is preferred that the movable arms and the base are formed by bending a single metal plate. Since the main portion of the actuator is formed by bending a single metal plate, its fabrication becomes easy and a mechanically strong actuator can be provided.
It is also preferred that the actuator is formed to have a spacing between the pair of movable arms slightly shorter than a width of the head slider to be caught, and that the catching step includes provisionally fixing the head slider between the movable arms by a pinching force of the movable arms. In this case, preferably, the catching step includes securely fixing the head slider to the movable arms by curing an adhesive after the provisional fixing.
It is preferred that the fixing step includes fixing the actuator and the support each other by adhering or by laser welding.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.